1) Field of the Invention
The present invention relates to smart patches and, more particularly, to a smart repair patch for monitoring the integrity of the repair patch.
2) Description of Related Art
Materials and structures employed in the aerospace industry and elsewhere may periodically require repair for in-service damage. Rapid inspection and repair of aircraft or ground vehicles are important for military and commercial applications in order to decrease down time. Temporary patch repairs of a metallic or composite structure are sometimes utilized to enable continuing use of the vehicle, such as an aircraft, until a permanent repair may be made. Temporary patches cost less than permanent repairs and can be installed very rapidly. In addition, temporary patches reduce down time and provide flexibility for utilizing the best schedule and cost options available.
However, confidence in the quality of the temporary repairs has decreased. In particular, temporary patches can detach from the structure without warning if the patches are not checked regularly. However, inspection of temporary patches tends to be costly in light of the time and labor required to perform the inspection. For example, a temporary patch inspection program may require that the patches be inspected after every flight for the first week, then every day for a week, and then weekly for a period of time. To avoid inspection costs, the user may apply a more costly temporary repair patch, choose a limited time window of temporary patch use, or choose to proceed with an immediate permanent repair; all of which decrease available repair options. Furthermore, conventional methods for inspecting temporary repair patches (e.g., tap testing) can be subjective and not provide quantitative data for time-based comparison. Various alternatives to inspect temporary repair patches employ electronic equipment which may be expensive, time-consuming, and require trained experts in order to use.
Repair patches have been developed that generally acquire data indicative of a structure and the repair patch itself. For example, U.S. Pat. No. 5,553,504 to Lyons et al. discloses an instrumented patch for repair of a structure. In particular, Lyons discloses an apparatus that includes a plurality of strain sensors integrally formed with a patch to be fixed to an area on the surface of a structure. The sensors monitor changes in the strain field in the patch-covered area for detecting crack formation and detection, as well as the structural integrity of the patch. Namely, anomalies, such as tears or holes in the patch, or partial detachment of the patch from the structure, can be detected by measuring changes in the strain field in the region of the patch-covered area with the strain sensors. There is a need for an improved system that includes a repair patch that is capable of not only repairing a structure, but also performing NDI on the repair patch itself.
It would therefore be advantageous to provide a system that is capable of both repairing and monitoring the integrity of the repair patch. In addition, it would be advantageous to provide a system that is capable of inspecting the repair patch effectively and efficiently. Furthermore, it would be advantageous to provide a system that is economical to manufacture and use.